Focused ion beam (FIB) system is one of the primary tools for examining, analyzing, and repairing processing layers while fabricating of integrated circuits. FIB systems facilitate analyzing defects on in-process wafers as well later diagnosing and correcting the process when a defect does occur. FIB systems are versatile instruments, able to perform a number of operations (including milling, gas assisted etching, deposition, imaging) in various applications as, for example, on-chip circuit modification, mask repair, micro-machining, FIB lithography, end-point detection, advanced circuit diagnostics for failure analysis, micro-manufacturing of objects with micron and submicron sizes, etc.
For example, FIB milling of cross-sections enables to expose underlying layers for observation and testing by removing covering material. The exposed layers may be examined using, for example, the imaging capability of the FIB system, using a scanning electron microscope (SEM) or transmission electron microscope (TEM), etc.
Various implementations of FIB for cross-section milling and further observation are disclosed, for example, in the following patent publications:
U.S. Pat. No. 5,093,572 (Hosono) discloses a scanning electron microscope for cross-section observation capable of cutting more accurately a cross-section of a specific portion of semiconductor wafer in a shorter time, and a cross-section observing method employing such a microscope. The scanning electron microscope includes an SEM column, an FIB column mounted together with SEM column, and a reflected-electron detector for detecting electrons to be reflected from the semiconductor wafer by scanning with an electron beam from the SEM. Thus, since a process of cutting a cross-section to be observed by scanning with an ion beam from FIB column, can be observed in real time by employing the reflected electrons of electron beam from SEM column, a specific portion of the cross section can be cut more accurately in a shorter time.
U.S. Pat. No. 6,211,527 (Chandler) discloses a method for making connections to conductors buried under dielectrics layers using a focused ion beam and an etch-assisting gas, the method allows a via to be milled to contact the conductor without substantial etching and degrading the conductor.
U.S. Pat. No. 6,641,705 (Phaneuf et al.) discloses a method of using a focused ion beam (FIB) apparatus for uniformly removing material, particularly crystalline material, from an area of a target by compensating for or altering the crystal orientation or structure of the material to be removed.
U.S. Pat. No. 6,670,610 (Shemesh et al.) assigned to the assignee of the present application, discloses a system and method for directing a miller. The system includes first images such as a scanning electron microscope, a stage for moving the object and a second imager and miller such as a focused ion beam generator. The object is images to locate a desired location in which the object is to be milled and a landmark that is utilized for directing the miller. The system can include additional steps of milling, analyzing and movement of the object.
U.S. Pat. No. 6,768,110 (Alani) discloses an ion beam milling system and method for electron microscopy specimen preparation, includes vacuum chamber housing ion guns and specimen in holder, with ion beam mask fixed to specimen surface so that no relative movement occurs during milling. The system also includes the ability to view the progress of the milling operation and may include an imaging device such as a light microscope which permits monitoring of the area of interest on a specimen as the specimen is milled.